Mobility and traceability of potentially toxic elements in soils after 500 years of mining: a case study of the Taxco de Alarcón mining site, southern Mexico.

Abstract

The concentrations of Potentially Toxic Elements (PTE) and the isotope composition of Pb in the soils of the Taxco de Alarcón region were analyzed to assess the impact of abandoned mine tailings on soils in this region. PTE concentrations in the soils exceeded the international recommended limits for Cd, Ni, Cu, Ba, Pb, Zn, and Mn. Additionally, phytoavailability and sequential extraction procedures values indicated the mobility of Pb-Zn-Mn and Pb-Zn-Mn-Cd, respectively, due to a high percentage in the more labile fractions. Environmental indices (e.g., EF, MPI, and RAC) revealed that the concentration of most soils is moderately to severely enriched in PTE, suggesting that erosion and dispersion of mine tailings are likely the main contributors to soil composition. Furthermore, the Pb isotope composition, combined with a Bayesian statistics-based model, indicates that mine tailings are the main source of Pb for soils. Although the soils in this mining region appear unaffected by mining waste, PTE concentrations and Pb isotope data indicate otherwise, highlighting that oxidation, erosion, and dispersion processes are impacting the soils. The geochemical features of these soils pose a danger to the environment and human health since they are often used for agricultural and livestock purposes, increasing PTE mobility into the food chain.